I want to curve an object like a roller coaster using a path
Important

Make sure your track model's origin is moved to align exactly on the edge of the model. The modifier will depend on the origin's Position to make duplicate and alignment.




Use the Array modifier to create copies of the track model.
Create a bezier curve representing the curve and length of track.
Add a Curve Deform Modifier and target the bezier path curve object.




The blend file ...



Extra Note
Instead of "Fixed Count" use "Fit Curve" on the array modifier Fit type drop down menu to improve control to the duplication of the mesh according to the length of the curve.